Ceramic coating compositions which are particularly useful in providing decorative and functional coatings for glass, chinaware and the like are well known. These compositions in general take the form of squeegee pastes or roll coat paints and they must have specific properties in order to have a working product. Especially important is the viscosity of the medium or vehicle used in producing the composition. Also important is the solids loading capacity (powder to oil ratio) of the paste materials made with the medium. Additionally, the rheology or viscosity profile of the squeegee paste or the roll coat paste is an important factor.
In general, the ceramic coating compositions are composed of a glass frit, a vehicle or medium and, optionally, a pigment. Typically, the composition in the form of a paste is applied to a substrate such as automotive glass by silk screen or other application technique and the coated substrate is heated or fired to fuse the glass frit and to volatilize the vehicle or medium, thereby firmly bonding the coating to the surface of the substrate.
The vehicles or mediums which have previously been employed in the ceramic coating compositions are typically organic and include compositions based on pine oils, vegetable oils, mineral oils, low molecular weight petroleum fractions, tridecyl alcohol and the like. The vehicles may be modified by addition of viscous resins such as vinyl resins, solvents, film formers such as cellulosic materials, and the like.
There is a need in the art for paste ceramic coating compositions which have a high solids content. This results in products having lower volatile organic content (VOC). The need for lower VOC products is particularly important in ceramic coating products which employ the lead-free glass frits since these products have a lower density.